When a guy who you have worked with for 2 months, but is not really a friend, gently places his hand on the back of your head during a goodbye hug?

I was leaving the office farewell party and was saying bye to all members of my group individually. I went upto him as well to say bye and he initiated the hug.

When a guy who you have worked with for 2 months, but is not really a friend, gently places his hand on the back of your head during a goodbye hug?
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